Among conventional IC chips, a high voltage IC chip is known as having an operating voltage range that exceeds +5 volts. These chips normally have dimensions larger than chips that operate at +5 volts and therefore, the manufacturing cost for the higher voltage IC chips is higher than the cost for the lower voltage chips. However, a conventional voltage conversion circuit for IC chips only operates between a high voltage of +3 volts to +5 volts. Also, it is not capable to convert an operating voltage to a voltage of below 0 volt.
In a conventional voltage conversion circuit for the 3 volts/+5 volts range, a low voltage of the circuit is maintained at 0 volt. In a conventional high voltage IC chip, the input voltage is shifted to the highest output or the lowest output voltage directly at the input interface. In this way, the logic circuit of the high voltage IC chip operates at the highest output or the lowest output voltage. In connection with the large voltage difference between the two voltages, a large area high voltage components must be used at respectively higher manufacturing cost. Furthermore, a conventional +3 volts/+5 volts voltage conversion circuit is limited to a low operating voltage at 0 volt. It cannot be used for a high voltage IC chip that operates at an operating voltage of below 0 volt.
It is therefore an object of the present invention to provide a voltage conversion circuit for IC chips that does not have the drawbacks of conventional voltage conversion circuits.
It is another object of the present invention to provide a voltage conversion circuit for IC chips that provides an operating voltage range of high voltage of higher than +3 volts and low voltage of lower than 0 volt.
It is a further object of the present invention to provide a voltage conversion circuit for IC chips capable of using low voltage components of smaller dimensions.
It is still another object of the present invention to provide a voltage conversion circuit for IC chips that is equipped with a voltage conversion circuit at the input terminal of the IC chip.
It is yet another object of the present invention to provide a voltage conversion circuit for IC chips that provides a low voltage to high voltage conversion circuit as an interface at the output terminal of the IC chip.
It is yet another further object of the present invention to provide a voltage conversion circuit for IC chips that does not occupy a large IC area and does not consume high power.
It is still another further object of the present invention to provide a voltage conversion circuit for IC chips that operates in an operating voltage range of low voltages below 0 volt.